As the advanced semiconductor fabrication process uses substrates of larger size, the heat treatment of substrates in an oven is considered. Under the trend, there is pointed out the problem that chemically amplified positive resist materials undergo substantial variations of pattern feature size due to the influence of varying temperature within the oven. Novolak resin-NQD base positive resist materials become attractive since they are relatively insensitive to temperature variations.
In the semiconductor fabrication process, a resist material is generally used to form a resist film on a support such as film, sheet, metal substrate or ceramic substrate. Since the surface of the support has been stepped as a result of circuit formation, the resist material which is used in later steps of the semiconductor fabrication process is required to form a uniform coating free of voids or defects on the stepped surface. When a liquid resist material is coated onto the stepped or uneven surface of a support, it is difficult to form a coating of uniform thickness. Voids are likely to form near steps. The liquid resist material is difficult to meet the requirement whereas a resist film is adequate for the purpose.
Only a few documents refer to positive tone resist films. Patent Document 1 discloses a dry film resist which is mainly intended for scum control, but insufficient to suppress void formation on a stepped support. Since the dry film resist is short of flexibility, it fails to fully conform to steps on the support surface. There is a strong desire for a positive resist film laminate which eliminates void formation when transferred to a stepped support.